So long as you remember
to show your working and get the units right, that's pretty much it for
GCSE - apart from one thing: average speed.

If we think about
the speed of a car during a journey from town to town, it'll vary hugely
throughout the journey. Sometimes the car will be stopped at traffic lights,
other times it'll be whizzing along a motorway. However, it's useful to
be able to work out the average speed over the whole journey.

Average speed
is really easy to work out: total distance
divided by total time for the journey.

Sometimes we're only
interested in how fast something's going, other times we need to know
which way it's going too. So physicists came up with the idea of velocity.

Velocity
is speed in a particular direction.

Thus
we could say that a car has a speed of 10 m/s, and go on to say that it's
velocity is 10 m/s northwards. if he car goes round a corner without speeding
up or slowing down, then it's speed hasn't changed - but it's velocity
has.